In the 1980s and early '90s, conservatives drank deeply from the well of cultural pessimism. Analysts looked at rising youth crime, welfare dependence and illegitimacy and concluded that our society was in deep, perhaps irreversible, decline. America, in Judge Robert Bork's vivid phrase, was "slouching towards Gomorrah."

The root cause was clear to many: Cultural decay is the natural result of family breakdown. "Illegitimacy," wrote Charles Murray, "is the single most important social problem of our time . . . because it drives everything else." And on this issue, the news was uniformly discouraging. "Every once in a while," argued Murray, "the sky really is falling."

The blessed disappointment of these expectations is the subject of "Crime, Drugs, Welfare -- and Other Good News," a groundbreaking essay by Peter Wehner and Yuval Levin in Commentary magazine. "Over the past fifteen years, on balance, the American family has indeed grown weaker," the authors argue, "but almost every other social indicator has improved." Crime rates have plunged, teen drug use and pregnancy have declined, educational scores are improving, welfare caseloads have fallen 60 percent, and the number of abortions has dropped.

On cultural issues, conservatives have been ambushed by hope. And Wehner and Levin provide two main explanations.

First, societies can, over time, recognize their own self-destructive tendencies and reassert old norms -- not just arresting decline but even reversing it. Many Americans, for example, have seen the damaging effects of divorce on children -- sometimes from the firsthand perspective of their own childhoods -- and divorce rates, especially among upper-income couples, have fallen. Over the decades the social wreckage of drug use has become undeniable -- and the social judgment on this practice has shifted from "stylish rebellion" to "suicidal idiocy." In many cases, our culture has benefited from the natural healing mechanism of simple sanity.

The second reason for this cultural renewal is bold, effective public policy -- welfare reform with time limits and work requirements; zero-tolerance approaches to crime; education reform that tests and requires basic skills; and comprehensive anti-drug efforts, including enforcement, treatment and education. In all these cases, good government and rational incentives have made a tremendous difference.

These social achievements challenge a number of assumptions.

Conservatives often assert that "culture is upstream from politics" -- meaning that issues of family, character and values are entirely beyond the reach of government. Some cultural conservatives have gone so far as to argue that cultural change will first require religious revival, a fourth Great Awakening. It turns out, however, that addressing some social problems does not require the preaching of a new John Wesley but the teaching of reading, the enforcement of public order and the encouragement of honest work. We cannot expect government to fulfill the duties of churches and synagogues. But we should expect it to fulfill the duties of government.

Conservatives often affirm the "law of unintended consequences" -- meaning that government reforms often leave us worse off than we started, so it is better not to start them at all. Some conservatives, for example, opposed welfare reform in the mid-1990s on the grounds that the culture of dependence was too ingrained to be changed by the shifting of incentives.

Wehner and Levin find that the law of unintended consequences, unlike the law of gravity, admits large exceptions. "Problems that may seem intractable at one moment -- violence and disorder, harmful and reckless conduct -- can yield, and yield quickly, to the right politics and to a determined citizenry. Human problems, products of human failings, can be addressed at least in part by human ingenuity."

And conservatives often assert that family breakdown leads inevitably to a new cultural barbarism. It is clearly not that simple. Families that shatter or never form can impose a hefty emotional and economic cost on children. But the products of these broken homes -- betrayed by failing schools and fed on video games, rap music and Internet porn -- have also been the heroes of Sept. 11, Afghanistan and Iraq. Human character, drawn out by duty, somehow survives a less than perfect culture.

There is still, as Edmund Burke might have said, plenty of ruin in our nation. But this cultural reversal of fortunes should remind dispirited conservatives of the role of hope in politics. Well-designed public policies can serve the common good and make our country stronger and more just. American society is more resilient than some imagined. Cultures are capable of change because men and women are capable of rational decision-making, unsuspected courage and even redemption.

And all these lessons confirm a larger lesson: Pessimism is an easy pose; hope is a moral virtue.